Parrots versus Possums

The swift parrot is one of Australia’s most charismatic birds, but it’s also one of its most endangered. Each year every swift parrot in the nation flies south to Tasmania to breed. Logging and land-clearing have decimated their habitat but conservation biologist Dejan Stojanovic has made the startling discovery of why the swift parrot numbers are plummeting so rapidly – they’re being eaten by the deceptively sweet sugar glider. In a race against time, Dejan and his team have raised $70,000 through social media to build nesting boxes to save the bird. Catalyst reporter Mark Horstman joins the tree-climbing scientists in the spectacular Tasmanian wilderness as they deploy the first of 1000 boxes.Photo credit: Henry Cook

TRANSCRIPT

Dr Dejan StojanovicFor me, when you're at the top of an enormous forest giant and you can see the ocean on one side and snow-capped mountains on the other, I would never take an office job.

NARRATIONBut all is not as tranquil as it seems.

Dr Dejan StojanovicSo, I climb trees and I see dead nest after dead nest after dead nest.

NARRATIONThere's a surprising war between two unlikely combatants - the showy swift parrot and the shy sugar glider. And the battle is all about real estate.

Mark HorstmanMagnificent trees like this Tasmanian blue gum are absolutely vital to the many animals that use its hollows to nest and breed. But it takes at least 150 years for these hollows to form, and that's the problem - there's just not enough of these old trees left.

NARRATIONOld-growth forest has been decimated by logging and land-clearing. In the fierce competition for dwindling real estate, the deceptively sweet sugar glider is literally eating the swift parrot out of house and home.

Dr Dejan StojanovicWe have to act because we've only got 16 years before the species is functionally extinct.

NARRATIONOf all the birds on the planet, there are only three migratory parrots. Endemic to south-east Australia, the swift parrot is one of them. Noisy, active and a voracious feeder, its estimated population has fallen to around 1,000 breeding pairs, making it one of Australia's rarest birds.

Dr Dejan StojanovicEvery swift parrot in the world flies to Tasmania in the summer to breed. So, there's this key moment in time when the entire population is funnelled into a tiny bottleneck which is Tasmania.

NARRATIONDuring the breeding season, they feed only on flowering blue gums and black gums. But these trees don't flower every year.

Dr Dejan StojanovicUnlike a lot of birds, swift parrots focus on a really variable resource, and so they move around the landscape. And so you can have hundreds of kilometres separating places where swift parrots breed.

Mark HorstmannSo, you know where they MIGHT be or they COULD go, but you don't know they're there until they actually turn up.

Dr Dejan StojanovicExactly.

NARRATIONFor Dejan and fellow researcher Matt Webb, this annual moving target makes swift parrots a challenge to study. Over the last decade, they've been monitoring 1,000 different sites every year across the eastern half of Tasmania.

Matt WebbOne of the really important things that come out of that work and the modelling that we've done is that really it's only small fraction of the breeding range that's actually available each year. And it's due to these flowering patterns.

NARRATIONAlthough it's just turned spring, it's still a bit early for swifties to arrive. Just in case, we check one of their favourite haunts, a park at Port Huon just south of Hobart.

Mark HorstmannThere's some movement up there.

Matt WebbThere! There!

Mark HorstmannWhat is it?

Matt WebbIt's swifties. First swifties of the year.

Mark HorstmannFair dinkum?

Matt WebbYeah.

Mark HorstmannI can't believe our luck.

NARRATIONThe new arrivals feed frenetically on black gum flowers.

Dr Dejan StojanovicOnce they pick an area where there's good flower, they then have a second requirement of old forest which has hollow-bearing trees, because swift parrots don't nest anywhere - they nest in tree hollows. But they don't just nest in any old tree hollow. They like a small entrance to exclude predators. They like a deep chamber of about 40cm or so, so that they can put their eggs and nestlings as far away as possible from the entrance. And they need about 12-15cm of floor space, so they can put three or four nestlings in there and mum can sit next to them without being too crowded.

NARRATIONOn top of that, the chances of finding just the right hollow, close to flowers, are low.

Dr Dejan StojanovicOur research has shown that, of the available tree-cavity resource, only about 5% of available hollows are suitable. Only one in eight mature trees actually fits the bill for swift parrots.

NARRATIONAlthough wildfires take a toll, it's industrial logging, land-clearing and firewood-harvesting that are most responsible for reducing the number of hollow-bearing trees.

Dr Dejan StojanovicAnd, I mean, not so long ago, this whole region would've been covered by amazing, wet eucalyptus forest - old-growth trees, 3-4m diameter is the average tree. But clearly what we're walking through now is, you know, not quite like that anymore - it's dominated by trees that are no thicker than toothpicks really. And, unfortunately, that old forest provided an incredibly rich resource for hollow-nesting birds like swift parrots.

NARRATIONWhen Dejan began studying the swift parrots' decline, he knew that habitat loss was involved, but it couldn't account for the carnage he began to see.

Dr Dejan StojanovicI came back one week and half of the nests had been killed, and female parrots had just been torn apart and egg fragments, and it was just a mess. He installed movement-sensitive cameras and trained them on the parrot hollows. What the cameras recorded was totally unexpected. To Dejan's astonishment, the culprits were sugar gliders. I love sugar gliders. Who doesn't love sugar gliders? But to see them as the perpetrator of these really grizzly predation events, it was shocking.

NARRATIONSugar gliders were devouring not only the eggs and the chicks, but the nesting females as well.

Dr Dejan StojanovicWe now, over five years of researching this phenomenon, have quantified that approximately half of the adult female swift parrots get eaten every year, and this level of predation is just so severe that the swift parrot population can't tolerate it.

NARRATIONHe's found a strong correlation between predation rates and loss of old-growth forest.

Dr Dejan StojanovicPlaces where old-growth has been reduced to as little as 20% of the available forest cover in an area, predation by gliders can reach 100%, which means every bird - dead, every nest - failed. In areas where the old-growth forest is much higher, survival for swift parrots can be higher than 90%.

NARRATIONWith less real estate to go round, there's increased competition for nesting space. But what's going on? Could it be that sugar gliders aren't supposed to be here? It's long been thought that sugar gliders were introduced from the mainland in the 1830s. But no-one knew for sure. Until now. Using tissues from museum specimens, Cat Campbell compared genes from the Tassie sugar glider with those from the big island.

Cat CampbellThe Tasmanian individuals that I sequenced are identical to individuals from the mainland found in Victoria and South Australia.

NARRATIONThe genetic evidence confirms that in Tasmania sugar gliders are an introduced animal outside their natural range. While sugar gliders are now common throughout the state, the good news for swift parrots is that they haven't made it to the surrounding islands, like here at Bruny.

Dr Dejan StojanovicSwift parrots that nest on the islands, on average, have extremely high success rates. In excess of 99% of the birds that nest on Bruny Island do really well.

NARRATIONAs it turns out, Bruny is also a safe haven for another threatened bird facing a similar plight to the swift parrot.

Mark HorstmannWith a name longer than its body, the forty-spotted pardalote is one of Australia's smallest birds. It lives only in Tasmania, it's endangered, its population is declining and it's now mostly restricted to just a few islands like here at Bruny Island.

NARRATION100 nesting boxes have been installed to provide more nesting opportunities for the vulnerable pardalote.

Dr Dejan StojanovicThey've had a really high rate of use, so at least half of those boxes get used annually by forty-spots. And there's clear evidence that pardalotes, A, will use boxes, B, can rear their nestlings successfully and C, can occupy new locations where they didn't use to be because of hollow-limitation.

NARRATIONThis successful tactic inspired Dejan's colleague and wildlife photographer Henry Cook to do something similar for swift parrots, Capitalising on the birds' charisma, Henry set up a crowd-funding campaign.

Henry CookIt seems a bit mad at first, but we wanted some serious numbers of nest boxes, because doing things in small amounts, not really worth it. So, we went for 1,000 nest boxes.

NARRATIONAnd enlisted support from some of Australia's foremost political cartoonists, like Jon Kudelka.

Jon KudelkaI think people tend to respond to a drawing sometimes more than being told about it or a photograph. And you kind of a give a personal view of what's going on, and, you know, put some words with the pictures.

Henry CookInitially set a target of 40 grand to crowd-fund, and we ended getting $73,000. $73,000 in eight weeks, but the first 40 grand was achieved in three days. The response from the public was just unbelievable.

NARRATIONThat crazy dream of 1,000 nest boxes has become a reality. 500 boxes for the forty-spotted pardalote and 500 for the swift parrot are now under construction. And today they're starting to be deployed on glider-free Bruny to give the birds a boost.

Mark HorstmanWhat's the highest you've climbed?

Dr Dejan StojanovicHigher than I'd admit to my mother on television.

NARRATIONBut even here, swift parrot habitat is still available for logging.

Mark HorstmannThis is nesting box No.1, the first of 500 new breeding boxes to be installed for the swift parrot. And this is in the safe neighbourhood of Bruny Island where there are no sugar gliders. The real challenge is across the water in mainland Tasmania.

NARRATIONThere, parrots have to contend with both logging and gliders.

Dr Dejan StojanovicBased on our models of population viability of the swift parrot, within three generations - which for the swift parrot is only 16 years - that rate of predation by sugar gliders on the nesting females is likely to lead to a population collapse of up to 94%.

NARRATIONWhile the nest boxes aren't yet glider-proof, they'll help Dejan and his team learn more about glider behaviour and buy time for the parrots. And they're going one step further to protect individual parrot nests in glider-infested areas. He's trialling lethal traps for sugar gliders, as used to control feral brush-tailed possums in New Zealand.

Dr Dejan StojanovicWell, this is the very first time that we've trialled this in Australia. It's a kill trap called Goodnature traps, and they're this ethical trap.

NARRATIONIt's early days, and first he must ensure the traps will only target gliders.

Dr Dejan StojanovicWhat's a bit of relief to me is to see that the pygmy possums are just walking past.

NARRATIONControlling sugar gliders is not a decision taken lightly. But that's the dilemma we face while swift parrot habitat continues to be lost.

Dr Dejan StojanovicThe swift parrot population appears to be in freefall and, as a conservation biologist, I have two options - I can continue to monitor them into extinction and do nothing, or we can investigate techniques that might work, may not necessarily be palatable to everybody, but might offer a solution to prevent the extinction of one Australia's most iconic species.

YOUR COMMENTS

Thanks for the previous reply. I have seen a camera in a large gumtree here at Big Roaring Beach, Dover near a spot where I know Swift Parrots were feeding and looking for nesting sites. Would very much like to know the results if any. (camera is now gone)

Nora Preston - 14 Jan 2016 3:41:46am

I think the Sugar Gliders will like those nest boxes they are putting up for the poor Swift Parrots. I'm surprised to hear these people say that the Sugar Gliders are eating the Swift Parrots, they aren't part of their diet. Sugar gliders eat the grubs under the bark of the trees and not any species of birds. If this is true, they should fix up what is missing in their diet and replace it for them, however, I still don't believe it.

"Forestry Tasmania is committed to protection of threatened species, and recognises that some swift parrot habitat coincides with some areas of public production forest.

Forestry Tasmania is very aware of the recent modelling predicting an extremely rapid decline in swift parrot numbers due to nest predation by sugar gliders, and also that sugar gliders are not present on Bruny Island.

In recognition of the unique circumstances of Bruny Island, the Government in consultation with Forestry Tasmania has decided to take a precautionary approach. Forestry Tasmania believes this is the appropriate response to the recent evidence and will not schedule any further harvesting on Bruny Island pending the completion of an evidence-based strategic species management plan for the conservation of swift parrot habitat in Tasmania."

PK - 25 Oct 2015 10:29:47am

Using the traps is going to be difficult, I looked up their web site, they are designed to specifically target the brush tailed possum and they are very effective (this is however a protected native in Tasmania), personally I don't love brush tail possums and would prefer the parrots, but I can see a big problem there.

Nora Preston - 14 Jan 2016 3:43:10am

They are naming the Sugar Gliders not Brush tails, and the Brush tails are gorgeous as well.

margaret hewitt - 24 Oct 2015 3:42:37pm

I watched Catalyst on the ABC and I would like some help because I have 6 Rosella nest boxes on our 3 acre house block I have filled the back yard with native trees. About 10 years ago I had masses of birds and the rosella's bred every year,then they stopped going in the boxes,I was happy to find the sugergliders thinking they only ate blossom and bark I have no little birds at all the only birds here now are bigger ones . Is there some way to have both what area does the sugarglider cover?

Joanna Postlethwaite - 22 Oct 2015 12:03:40pm

Just wanted to let Matt know that there are Swift Parrots at Big Roaring Beach 8kms east of Dover and I have been photographing them. I saw two nesting sites being checked out by the parrots and then these sites taken over by starlings. Is this known, and is it a problem ? I would be very interested to know.

Moderator: Here's a response to your query from Matt. Thanks for this report. We have recorded swift parrots in this area as part of our monitoring program this year and it is a very regularly used site. We have recorded starlings taking over nests before (including this year on Bruny Island). Records of this occurring are very important and I will follow this up. Unfortunately there are many starlings in this area because it is surrounded by farmland. They can be quite vicious little birds destroying eggs, killing female parrots and building nests on top of them, and also killing chicks!

By the way, starlings are also a problem for the Orange-bellied Parrot

Rae Faulkner - 21 Oct 2015 9:32:00am

Just a thought probably already thought of but here it is anyway. To help protect the parrot in Tasmania from the sugar glider what about a fine mesh wire with a small hole in the centre, so only the parrot can get in, attached to the tree over the hole of existing nesting sites.